Shock absorbing electrical connector



Jan. 3, 1967 J. L. LE- BAIGUE 3,296,387

SHOCK ABSORBING ELECTRICAL CONNECTOR Filed Nov. 2, 1964 INVENTOR. JACQUES L. LeBAlGUE BY if f4 W HIS ATTORNEY United States Patent 3,296,387 SHOCK ABSORBING ELEQTRHCAL CONNETOR Jacques L. Le Baigue, Westbury, N.Y., assignor to Electrolux Corporation, Fairfield, Conn., a corporation of Delaware Filed Nov. 2, 1964. Ser. No. 493,041 4 Claims. (Cl. 191-124) My invention pertains, in general, to electrical connectors for use with cordwinders; and, more particularly, to an electrical connector, such as a male plug, which includes a bumper integrally formed with the body portion of the connector for absorbing the shock produced by the sudden arresting of the rotation of the cordwinders drum when the electric cord to which the connector is attached is fully retracted.

Cordwinders for flexible electric cords are usually provided with a spring motor which is wound by the rotation of the winding drum during withdrawal of the cord, the spring motor thus being conditioned to rotate the drum for rewinding the cord. An ordinary spring motor having a spiral spring produces a maximum torque when fully wound, the torque dropping ofi as the spring becomes unwound. Consequently, the torque approaches a minimum value as the cord becomes fully rewound, with the result that the drum is rotating at a minimum speed at the end of the rewinding. The rotation of the drum is usually stopped by the plug on the electric cord striking the cordwinder housing, it being too large to pass through the cord opening in the housing, or by a bumper of relatively hard material slidably mounted on the cord, in the latter case the plug being relied on to limit the displacement of the bumper along the cord.

However, an improved rewinding action is obtained if a Negator spring is employed to drive the winding drum. A spring of this nature is capable of producing a constant torque throughout the entire rewinding operation and consequently the winding drum does not slow down, but rather tends to increase its speed of rotation to a maximum value at the time the cord becomes fully rewound. This greatly increases the impact of the plug against the housing of the cordwinder, with the result that the electrical connection between the cord and the plug may be quickly damaged.

Therefore, one object of my invention is to incorporate a shock absorbing member directly in an electrical connector, such as a male plug, for the purpose of preventing damage to the electrical connection between the cord and connector when the connector strikes the cordwinder housing at the time the cord is fully retracted into the housing. Thus, I eliminate the need, and expense, of supplying the separate bumper element which heretofore has been required for protective purposes.

Another object of my invention is to provide an easily fabricated connector and cord assembly; said connector comprising a body and shock absorbing member which are molded as a unit about a subassembly comprising an electric cord having contact elements connected to the conductors thereof and a strain relief element crimped to the cords jacket and embedded in the connectors body during the molding operation.

Further objects and advantages of my invention will be apparent from the following description considered in connection with the accompanying drawings which form part of this application and of which;

FIG. 1 is a eross-sectional-view of a cordwinder including an electric plug according to one embodiment of my invention and the plug is shown at the instant it strikes the cordwinder housing;

FIG. 2 is a cross-sectional view taken on the line 22 of FIG. 1;

FIG. 3 is a view of a longitudinal cross-section of the 32%,387 Patented Jan. 3, 1967 electric plug of my invention shown prior to striking the cordwinder housing; and

FIG. 4 is a cross-sectional view taken along the section line 4-4 in FIG. 3 and showing the electric plug at the instant it makes impact with the cordwinder housing, in the same manner as shown in FIG. 1.

Referring to the drawings, reference character 10 designates the housing of a cordwinder. Integral with or secured to the housing 10 is a central hollow shaft 12 which forms the inner race of a ball bearing 14. The outer race 16 of the bearing is secured in the hub 20 of a reel or winding drum 22. A flexible electric cord 24 has one end secured to the drum 22 and is adapted to be wound up thereon, as is shown in FIG. 1. The cord 24 extends through 21 preferably elongated opening 26 defined within the raised wall portion Ilia formed in the housing 10 in radial alignment with the drum 22 and the outer end of the cord is electrically and mechanically connected to the electric plug 28 which is provided by my invention.

Rotatably mounted within the housing 10 on a shaft 40 is a spool 42 around which is wound a Negator spring 44. The opposite end of spring 44 is secured to the hub 20 of the drum 22, as by the rivet 46. This spring is so formed that it tends to wrap itself tightly around the spool 42. However, when the reel 22 is rotated in a clockwise direction, as by pulling the cord 24 outwardly through the opening 26, the spring 44 is unwound from the spool 42 and is Wound in a reverse direction around the hub 20, and the length of the spring is so chosen with respect to the length of the cord that when the latter is completely unwound from the drum 22 most of the spring is unwound from the spool 42 and Wound up on the hub 20.

Under these conditions, the spring tends to rewind itself around the spool 42 and in doing so exerts a torque tending to rotate the drum 22 in a counterclockwise direction, and when the drum is released the spring causes it to rotate in this direction so as to retract and wind up the cord 24. Due to the nature of the spring 44, as above mentioned, the torque exerted thereby is the same, regardless of the amount of spring remaining on the spool 42, throughout the entire rewinding operation. The more the cord is rewound, the less friction there is between the remaining unwound portion of the cord and the surface, usually the floor, across which it is dragged during the rewinding and hence there is a tendency for the winding drum to increase its speed of rotation. This means that the cord is traveling at a maximum speed, which may amount to 20 miles per hour, when it becomes fully rewound. Also, practically all of the cord being wound on and rotating with the drum, the mass and inertia of the latter is at a maximum, and experience has proved that if a conventional plug is relied upon to stop the drum 22, the resulting shock is sufficient to sever the plug from the cord after a relatively few operations.

A cross-sectional view, somewhat enlarged, of the electric plug 28 in accordance with my invention is shown in FIG. 3. In this view the cord 24, having the plug 23 at one end, is illustrated as being retracted toward, but not having reached, the cordwinder housing 10.

As illustrated, the plug 28 is comprised of: a body 30 molded from a suitable elastomeric material such as vinyl plastic, rubber, or the like; a shock-absorbing disc-like collar 32 integrally formed with the body 30 and being of the same elastomeric material; the pair of contact elements 34, or blades, embedded in the body 36 and connected with the conductors 36 which are within the jacket 33 of the cord 24; and the strain relief member 46 which is firmly crimped about a short length of electrical insulating tape 48 which has been wrapped around and bonded to the cords jacket 38.

To achieve the plug and cord assembly shown in FIGS. 3 and 4 the bared copper strands of the two conductors 36 are electrically connected to the respective blades 34. Afterward the adhesive insulating tape 48 is wrapped around the end portion of the jacket 38. Then the metallic strain relief element 46 is crimped around the tape 48 and exerts a relatively high pressure on the cords jacket 38. Thus, a strong mechanical connection between the jacket 38 and element 46 is assured and, advantageously, the tape 48 protects the jacket 38 from being pierced by the metallic strain relief element 46 during the crimping operation.

As indicated in FIGS. 3 and 4 the relief element 46 has a projecting element 46a integrally formed therein. This element 46a may have a generally semicircular crosssection and serves the purpose of transmitting a pulling force applied to the cord jacket 38 directly to the body portion 3i) of the plug.

As shown in FIG. 4 each of the blades 34 is formed by bending part of a long blade element back on itself and further bending a portion of the blade element to form a projection 34a which is directed at a right angle to the blade 34. These projections 34a also serve as strain relief elements; i.e., they transmit pulling forces applied to the blades 34 when the plug is pulled out of a female receptacle directly to the body portion 30 of the plug.

After assemblying the taped cord, blades and strain relief elements, in the manner hereinbefore described, the entire assembly is placed in a mold which conforms to the shape of the plugs body 30 and shock absorbing collar 32. Thereafter the mold is filled with a substance which when cured has suitable elastic properties; e.g., vinyl plastic, rubber, or the like.

FIGS. 1, 2 and 4 show how the collar 32 deforms to absorb shock when the plug 28 strikes the wall a of the housing 10. As a result of the collars bending (FIG. 4) a relatively small part of the impact force is transmitted to the plugs body 30 and, therefore, the connection between the cord 24 and the plug body 30, effected lgy the strain relief element 46, receives a minimal inpact orce.

As is shown in FIGS. 3 and 4 there is provided a sufficient space between the face 30a of the body 30 and face 32a of collar 32 so that at high impact forces the face 32a of the collar can bend toward face 30a through a substantial are without touching face 30a. in fact in the particular embodiment shown at FIGS. 3 and 4 a portion of the face 32a could bend until it about lies fiat on the surface 30b of body 30 without touching the face 30a at all.

While I have shown one more or less specific embodiment of my invention, it is to be understood that this has been done for the purpose of illustration only and that the scope of my invention is not to be limited thereby, but is to be determined from the appended claims.

What I claim is:

1. An electrical connector adapted for use with an electric cord which includes a plurality of conductors situated within a tubular dielectric jacket and is arranged for retraction into a cordwinder housing through an opening in the housing by being wound on a drum in the housing by a substantially constant torque spring motor which rotates said drum, said connector comprising an elastic body of dielectric material, a plurality of electrical contact elements, each contact element having a terminal portion thereof embedded in said body and connected to a different one of said conductors, a strain relief element secured to an end section of the cords jacket and embedded together with said end section in said body, said body including an integral elastic collar portion near that end of the body which receives said cord, said collar portion extending radially outward from the surface of said body and being normally disposed in a plane which is perpendicular to the longitudinal center- .line of the cord, said collar portion being larger than said opening in the housing so that at the instant said cord is fully retracted into the housing said collar portion contacts that portion of the housing adjacent said opening, arresting retraction of the cord, and flexes toward the surface of said body thereby absorbing the impact of said contact whereby a relatively small force is transmitted through said body to the strain relief element effecting the connection between the cord and the body.

2. A male electric plug for an electric cord which has a plurality of conductors situated within a tubular dielectric jacket and is arranged for retraction into a cordwinder housing through an opening in the housing by being wound on a drum in the housing by a substantially constant torque spring motor which rotates said drum, said male plug comprising an elastic body of dielectric material, a plurality of blades protruding from said body, each blade having a terminal portion thereof embedded in said body and connected to a different one of said conductors, a strain relief element secured to an end section of the cords jacket and embedded together with said end section in said body, said body including a relatively thin elastic annular collar portion near that end of the body which receives said cord, said collar portion extending radially outward from the surface of said body and being normally disposed in a plane which is perpendicular to the longitudinal centerline of the cord, said collar portion being larger than said opening in the housing so that at the instant said cord is fully retracted into the housing said collar portion contacts that portion of the housing adjacent said opening, arresting the cords retraction, and flexes toward the surface of said body thereby absorbing the impact of said contact whereby a relatively small force is transmitted through said body to the strain relief element effecting the connection between the cord and the body.

3. An electrical connector adapted for use with an electric cord including a plurality of conductors situated within a tubular dielectric jacket, said cord being adapted for retraction into a cordwinder housing through an opening in the housing by being wound on a drum in the housing'by a substantially constant torque spring motor Which rotates said drum, said connector comprising: an elastic body of dielectric material havinge two axially-aligned contiguous body portions of different cross-sectional areas and a thin elastic annular disc integral with and extending radially outward from the body portion having the smaller crosssectional area, said contiguous body portions defining at their juncture an annular wall surface which faces said disc, said disc being spaced from said wall surface by a distance which is suflicient to permit the disc to flex toward said wall surface and make contact with the surface of the body portion with Which said disc is integral without touching said wall surface, a plurality of electrical contact elements, each contact element having a terminal portion embedded in the body portion having the larger crosssectional area and connected to a different one of said conductors, and strain relief means secured to an end section of said jacket and embedded together with said end section in said body, said strain relief means being embedded in both body sections whereas the substantial portion of said end section is embedded in the body section of smaller cross-sectional area; said disc being normally disposed in a plane which is perpendicular to the longitudinal centerline of the cord and being larger than said opening in the housing so that at the instant the cord is fully retracted into the housing said disc contacts that portion of the housing adjacent the opening, arresting the cords retraction, and flexes toward said annular wall surface thereby absorbing the impact of the contact whereby a relatively small force is transmitted through said body to the strain relief means which effects the connection between the cord and body.

4. In combination with an electric cord including a plurality of conductors situated within a tubular dielectric jacket, said cord being adapted for retraction into a cord 5 Winder housing through an opening in the housing by being wound on a drum in the housing by a substantially constant torque spring motor which rotates said drum, an electrical connector receiving an end of the cord, said connector comprising an elastic body of dielectric material, a plurality of electrical contact elements, each contact element having a terminal portion thereof embedded in said body and connected to a difierent one of said conductors, a strain relief element secured to an end section of the cords jacket and embedded together with said end section in said body, said body including an integral elastic collar portion near that end of the body which receives said cord, said collar portion extending radially outward from the surface of said body and being normally disposed in a plane which is perpendicular to the longitudinal centerline of the cord, said collar portion being larger than said opening in the housing so that at the instant said cord is fully retracted into the housing said collar portion contacts that portion of the housing adjacent said opening, arresting the cords retraction, and flexes toward the surface of said body thereby absorbing the impact of said contact whereby a relatively small force is transmitted through said body to the strain relief element effecting the connection between the cord and the body.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 494,7236 7/1953 Canada.

OTHER REFERENCES German printed specification, 836,519, Himmler et al., April 15, 1952.

20 ARTHUR L. LA POINT, Primary Examiner.

S. T. KRAWCZEWICZ, Examiner. 

1. AN ELECTRICAL CONNECTOR ADAPTED FOR USE WITH AN ELECTRIC CORD WHICH INCLUDES A PLURALITY OF CONDUCTORS SITUATED WITHIN A TUBULAR DIELECTRIC JACKET AND IS ARRANGED FOR RETRACTION INTO A CORDWINDER HOUSING THROUGH AN OPENING IN THE HOUSING BY BEING WOUND ON A DRUM IN THE HOUSING BY A SUBSTANTIALLY CONSTANT TORQUE SPRING MOTOR WHICH ROTATES SAID DRUM, SAID CONNECTOR COMPRISING AN ELASTIC BODY OF DIELECTRIC MATERIAL, A PLURALITY OF ELECTRICAL CONTACT ELEMENTS, EACH CONTACT ELEMENT HAVING A TERMINAL PORTION THEREOF EMBEDDED IN SAID BODY AND CONNECTED TO A DIFFERENT ONE OF SAID CONDUCTORS, A STRAIN RELIEF ELEMENT SECURED TO AN END SECTION OF THE CORD''S JACKET AND EMBEDDED TOGETHER WITH SAID END SECTION IN SAID BODY, SAID BODY INCLUDING AN INTEGRAL ELASTIC COLLAR PORTION NEAR THAT END OF THE BODY WHICH RECEIVES SAID CORD, SAID COLLAR PORTION EXTENDING RADIALLY OUTWARD FROM THE SURFACE OF SAID BODY AND BEING NORMALLY DISPOSED IN A PLANE WHICH IS PERPENDICULAR TO THE LONGITUDINAL CENTERLINE OF THE CORD, SAID COLLAR PORTION BEING LARGER THAN SAID OPENING IN THE HOUSING SO THAT AT THE INSTANT SAID CORD IS FULLY RETRACTED INTO THE HOUSING SAID COLLAR PORTION CONTACTS THAT PORTION OF THE HOUSING ADJACENT SAID OPENING, ARRESTING RETRACTION OF THE CORD, AND FLEXES TOWARD THE SURFACE OF SAID BODY THEREBY ABSORBING THE IMPACT OF SAID CONTACT WHEREBY A RELATIVELY SMALL FORCE IS TRANSMITTED THROUGH SAID BODY TO THE STRAIN RELIEF ELEMENT EFFECTING THE CONNECTION BETWEEN THE CORD AND THE BODY. 